Summary

This week, physicists working with a $2 billion cosmic ray detector aboard the International Space Station confirmed a previously reported excess of antiparticles from space that could emanate from dark matter, the mysterious stuff whose gravity binds the galaxies. If so, the observation could help scientists determine the nature of dark matter. But the excess measured by the Alpha Magnetic Spectrometer could also be subatomic exhaust from a pulsar or some other mundane astronomical object. And determining which explanation is correct may require entirely different types of experiments and could take years.